Japanese Cannabis Users Rarely Progressed to Other Drugs, Challenging the Gateway Hypothesis | Research

The takeaway

Among 3,900 Japanese cannabis users surveyed, cannabis was typically the third substance tried (after alcohol and tobacco), and nearly half who reported it as their third drug did not use any other substances afterward.

Drug policy researchers and anyone interested in the gateway drug hypothesis.

0.08 odds of progressing from cannabis to methamphetamine

What the researchers found

Tobacco and alcohol were the most common initial substances, with cannabis typically third. The odds of progressing from cannabis to other substances were low: alcohol 1.25, tobacco 0.77, methamphetamine 0.08, other illicit drugs 0.78. Nearly half of those who reported cannabis as their third drug did not use other substances afterward.

Why it matters

Japan maintains some of the strictest cannabis laws globally, making this a unique context for testing the gateway hypothesis. Even in a prohibitionist setting, cannabis rarely led to harder drug use, suggesting the "gateway" pattern is not an inherent property of cannabis itself.

The numbers in context

N = 3,900. 81.5% male. Largest age group: 20-24. Cannabis typically 3rd substance after alcohol and tobacco. Odds of post-cannabis use: methamphetamine 0.08, other illicit 0.78, tobacco 0.77, alcohol 1.25. ~50% used no other drugs after cannabis.

How the study worked

Anonymous online survey of 3,900 individuals reporting lifetime cannabis use in Japan, recruited via social media in January 2021. Substance use progression was visualized using a Sankey diagram. Odds ratios calculated for likelihood of using other substances following cannabis use.

What this study cannot tell us

Online convenience sample may over-represent younger, tech-savvy users. Self-reported data may be affected by recall bias. Japan's strict drug enforcement may suppress progression to other drugs through deterrence rather than disproving gateway mechanisms. Social media recruitment introduces selection bias.

How to read the evidence

Large survey with quantified progression odds, but online convenience sample and self-report introduce bias. Moderate evidence for the Japanese context.

When this study was published

Published in 2025 with 2021 survey data.

The bigger picture

The gateway drug hypothesis has been a cornerstone of drug prohibition policy worldwide. This study from Japan, where cannabis use carries severe legal penalties, finds little support for the theory even in a context where cannabis users might be more risk-tolerant than in lenient jurisdictions.

Questions still open

Would results differ in countries with legal cannabis access? Does Japan's strict enforcement suppress drug progression that might otherwise occur?

Common questions

Is cannabis a gateway drug?

This study found little support for the theory in Japan. Cannabis users had very low odds of progressing to harder drugs, and nearly half used no other substances after cannabis.

Why study this in Japan specifically?

Japan has extremely strict cannabis laws, so if the gateway effect were real, it might be most visible in a context where cannabis users are already demonstrating willingness to break drug laws. The lack of progression even here weakens the gateway argument.

Read the original research

Revisiting the Gateway Drug Hypothesis for Cannabis: A Secondary Analysis of a Nationwide Survey Among Community Users in Japan.

Neuropsychopharmacology reports, 45(3), e70033

View on PubMed ↗Publisher’s paper ↗

Citation

Masataka, Yuji; Katayama, Munenori; Umemura, Futaba; Sugiyama, Takeshi; Miki, Naoko; Akahoshi, Yoshiyuki; Oka, Chihiro; Asahi, Takashi; Matsumori, Takashi; Takumi, Ichiro; Murata, Hidetoshi; Matsumoto, Toshihiko. (2025). Revisiting the Gateway Drug Hypothesis for Cannabis: A Secondary Analysis of a Nationwide Survey Among Community Users in Japan.. Neuropsychopharmacology reports, 45(3), e70033. https://doi.org/10.1002/npr2.70033